The quote "Be afraid, be very afraid" is not from the movie 'Halloween'. This line is from the 1986 horror film 'The Fly'.
'The Fly' is a 1986 horror film directed by David Cronenberg. It stars Jeff Goldblum as a scientist who accidentally merges with a fly during an experiment gone wrong. The film has become a cult classic and is known for its memorable lines, such as "Be afraid, be very afraid".